JP2817824B2 - Electrophotographic photoreceptor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photoreceptor, and more particularly to an electrophotographic photoreceptor made of an organic material and having excellent stability in characteristics when used repeatedly.

[0002]

2. Description of the Related Art Conventionally, as an electrophotographic photoreceptor (hereinafter also simply referred to as a photoreceptor), an inorganic photoreceptor using an inorganic photoconductive material such as selenium, a selenium alloy, zinc oxide or cadmium sulfide as a photosensitive material. Has been widely used. On the other hand, an organic photoreceptor made of an organic material using an organic photoconductive substance has been developed and put to practical use, focusing on advantages such as flexibility, thermal stability, film forming property, and low cost. . For example, poly-N-vinylcarbazole and 2,4
A photoreceptor comprising 7-trinitrofluoren-9-one (U.S. Pat. No. 3,484,237), a photoreceptor containing an organic pigment as a main component (JP-A-47-37543), and a eutectic complex comprising a dye and a resin are used. Photoreceptor containing main component
No. 10735). Such an organic photoreceptor
Although it has many advantages as described above, it has not been widely used because it is inferior to inorganic photoreceptors in sensitivity, stability of characteristics and durability, but in recent years it has excellent charging properties and sensitivity. Photoconductors have been developed and are rapidly spreading.

[0003]

A photoreceptor is repeatedly used in an electrophotographic image forming process, and is required to always have stable photoreceptor characteristics. However, as for such characteristic stability, at present, organic photoreceptors have not yet sufficiently responded to market demands. That is, with repeated use, there is a problem that a decrease in potential, a rise in residual potential, a change in sensitivity, and the like occur, resulting in a decrease in quality of an output image, making the image unusable.

An object of the present invention is to solve the above-mentioned problems and to provide an organic photoreceptor excellent in stability of photoreceptor characteristics, especially in potential stability when used repeatedly. .

[0005]

According to the present invention, there is provided an electrophotographic photosensitive member comprising a conductive substrate and a photosensitive layer containing a charge generating substance and a charge transporting substance. A photoreceptor provided with a photosensitive layer containing at least one of the indole compounds represented by the following general formula (I) and at least one of the benzidine compounds represented by the following general formula (II) as a transport substance. It is solved by.

[0006]

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[In the formula (I), R1 and R2 each represent a hydrogen atom, an alkyl group having 1 to 9 carbon atoms, an aralkyl group or an aryl group, and R3 represents a hydrogen atom or a carbon atom. Represents any one of the number 1 to 3 alkyl groups, alkoxyl groups, and halogen atoms. ]

[0008]

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[In the formula (II), Z1 represents a hydrogen atom or an alkyl group having 1 to 2 carbon atoms, and Z2 and Z3
Represents a hydrogen atom, an alkyl group having 1 to 2 carbon atoms, or a halogen atom, respectively. The photosensitive layer may have either a single layer containing a mixture of a charge generating substance and a charge transporting substance or a laminate of a charge generating layer containing a charge generating substance and a charge transporting layer containing a charge transporting substance.

As the charge generating substance, for example, a disazo pigment or an X-type metal-free phthalocyanine is preferably used. Furthermore, an undercoat layer may be provided between the conductive substrate and the photosensitive layer as needed.

[0011]

The charge transport material is a mixture of the indole compound represented by the general formula (I) and the benzidine compound represented by the general formula (II). ), Which is superior in the stability of photoreceptor characteristics, particularly the potential stability when used repeatedly, as compared with the case where the indole compound represented by the formula (1) or the benzidine compound represented by the formula (II) is used alone. You can get the body.

[0012] The effect obtained by using a mixture of the above two is that regardless of the constitution of the photosensitive layer, the photosensitive layer is a single layer containing a mixture of a charge generating substance and a charge transporting substance, or
Any structure of a stack of a charge generation layer containing a charge generation material and a charge transport layer containing a charge transport material may be used. In addition, the above-mentioned effects are not changed even if an intermediate layer is interposed between the conductive substrate and the photosensitive layer, and the film forming property of the photosensitive layer is improved, the adhesiveness between the conductive substrate and the photosensitive layer is improved, It is possible to provide an undercoat layer for improving the characteristics.

As the charge generating substance, for example, X-type non-metallic phthalocyanine and disazo pigments can be used, which is preferable since a highly sensitive photoreceptor can be obtained.

[0014]

The following are specific examples of the indole compound represented by the above general formula (I).

[0015]

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[0016]

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Specific examples of the benzidine compound represented by the general formula (II) are as follows.

[0018]

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[0019]

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The photoreceptor of the present invention contains at least one kind of the above-mentioned indole compound and at least one kind of the benzidine compound as a charge transport material in the photosensitive layer. There are two types shown in FIGS. 1 and 2 depending on the layer configuration. FIG. 1 is a conceptual cross-sectional view of one embodiment of the photoreceptor of the present invention.
A charge generating layer 22 composed of a charge generating substance 21 and a binder resin, and a charge transporting layer 24 composed of a binder resin containing an indole compound and a benzidine compound as a charge transporting substance 23 are sequentially formed via an undercoat layer 3. Laminated photosensitive layer 2
a is a function-separated type photosensitive member provided with a. The photoconductor of this configuration is generally used in a negative charging system.

FIG. 2 is a conceptual cross-sectional view of another embodiment of the photoreceptor of the present invention, in which a charge generating material 21 and an indole as a charge transporting material 23 are provided on a conductive substrate 1 via an undercoat layer 3. This is a single-layer type photoconductor provided with a single-layer photosensitive layer 2b made of a binder resin containing a compound and a benzidine compound. In addition, the undercoat layer 3 in FIGS.
Is provided as needed and may not be provided.

The conductive substrate 1 serves as a photoreceptor electrode and at the same time serves as a support for the other layers, such as aluminum, an aluminum alloy, stainless steel or the like, or glass or resin. The surface of which is subjected to a conductive treatment is used. The undercoat layer 3 is provided between the conductive substrate and the photosensitive layer and has a function of increasing the barrier function and the adhesiveness of the carrier, if necessary, and includes casein, polyvinyl alcohol, polyvinyl methyl ether, It is formed of poly-N-vinylimidazole, ethyl cellulose, ethylene-acrylic acid copolymer, phenol resin, polyamide, polyurethane, gelatin, aluminum oxide, or the like. The thickness of the undercoat layer is preferably in the range of 0.05 μm to 20 μm, particularly preferably in the range of 0.05 μm to 10 μm.

The charge generating layer 22 is prepared by dispersing the charge generating substance 21 together with a binder resin in an amount of 0.3 to 2 times the amount thereof in a solvent using a homogenizer, an ultrasonic wave, a ball mill, a sand mill, a paint shaker, or the like. Is formed by coating and drying the dispersion. The film thickness is 0.01
The range of μm to 3 μm, particularly 0.05 μm to 1 μm is preferred. Metal-free phthalocyanine,
Phthalocyanine compounds such as titanyl phthalocyanine,
Various pigments such as azo, quinone, indigo and the like, dyes such as cyanine, squarylium, azurenium and pyrylium compounds are used. A suitable substance is selected and used according to the wavelength region of light used for exposure. Examples of the binder resin include polyvinyl butyral, polyarylate, polycarbonate, polyester, phenoxy resin, polyvinyl acetate, epoxy resin, acrylic resin, polyacrylamide resin, polyamide, polyvinyl pyridine, cellulose, urethane resin, casein, polyvinyl alcohol, and polyvinyl. Resins such as pyrrolidone can be mentioned. In addition, as a solvent, methanol, ethanol,
Alcohols such as isopropyl alcohol; ketones such as acetone, methyl ethyl ketone and cyclohexanone; amides such as N, N-dimethylformamide and N, N-dimethylacetamide; tetrahydrofuran;
Ethers such as dioxane, ethylene glycol dimethyl ether, dimethoxyethane and propylene oxide; esters such as methyl acetate, ethyl acetate and dimethyl carbonate; aliphatic hydrogen halides such as chloroform, dichloromethane, dichloroethylene and trichloroethylene, or benzene , Toluene, xylene,
Aromatics such as monochlorobenzene can be used.

The charge transport layer 24 is formed by dissolving the above-described indole compound and benzidine compound as the charge transport material 23 together with a suitable binder resin in a solvent, applying the solution, and drying the solution. The film thickness is 10 μm
-50 μm, particularly preferably 15 μm-40 μm. The total amount of the indole compound and benzidine compound in the charge transport layer is preferably in the range of 30% by weight to 70% by weight, particularly preferably 40% by weight to 60% by weight, based on the total solid content in the charge transport layer. The mixing ratio of the indole compound and the benzidine compound is 5:95 to 95: 5, preferably 60:40 to 20:80 by weight. As the binder resin, for example, acrylic resin, polyarylate, polyester, polycarbonate, polystyrene, acrylonitrile-styrene copolymer, polyvinyl butyral, polyvinyl formal, polyacrylamide, polyamide and the like can be used. Further, the same solvent as that used for the charge generation layer can be used.

The single-layer photosensitive layer 2b shown in FIG.
A mixture of an indole compound and a benzidine compound as the charge transport material 23 in an amount of 1 and 2 to 10 times the amount thereof is dissolved and dispersed in a suitable solvent together with a suitable binder resin,
It is formed by applying and drying the liquid. The film thickness is preferably in the range of 10 μm to 40 μm, particularly preferably 15 μm to 25 μm.

Hereinafter, specific embodiments of the present invention will be described, but the present invention is not limited to the following embodiments. Parts in Examples are parts by weight. Example 1 A conductive substrate had a length of 30 mm, a width of 30 mm, and a thickness of 1 mm.
Was prepared. On this plate, a polyamide resin (“Amilan CM8000” manufactured by Toray Industries, Inc.) 4.5
Of the solution was dip-coated with 150 parts of methanol, and dried at 90 ° C. for 20 minutes to form an undercoat layer having a thickness of 0.2 μm.

Next, 2 parts of a disazo pigment having the following structural formula as a charge-generating substance, 2 parts of a polyester resin (“Vylon 200” manufactured by Toyobo Co., Ltd.) as a binder resin, and 90 parts of cyclohexanone were mixed, and the mixture was mixed with a sand grinder. For 6 hours. This dispersion was diluted with 60 parts of tetrahydrofuran to prepare a coating solution, which was dip-coated on the undercoat layer, dried at 90 ° C. for 20 minutes, and dried to a thickness of 0.4 μm.
Was formed.

[0028]

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Subsequently, the compound No. 1 as a charge transport material was used. 1.5 parts of the indole compound of Formula 5 and the compound N
o. The benzidine compound (1.5 parts) was dissolved in 30 parts of tetrahydrofuran together with 3 parts of a bisphenol Z-type polycarbonate resin (number average molecular weight: 50,000) as a binder resin to form a coating solution. Coating was performed with a bar, and the coating was dried at a temperature of 100 ° C. for 20 minutes to form a charge transport layer having a thickness of 20 μm. Thus, a laminated photoconductor having the configuration shown in FIG. 1 was produced.

Example 2 In Example 1, the compound N was used as a charge transport material.
o. 5 and 2.1 parts of the compound No. 5
A photoconductor was prepared by the same way as that of Example 1 except that 0.9 parts of benzidine compound of No. 12 was used. Example 3 In Example 1, the compound N was used as a charge transport material.
o. No. 5 and 0.3 part of the indole compound.
A photoconductor was prepared by the same way as that of Example 1 except that 2.7 parts of benzidine compound of No. 12 was used.

Example 4 In Example 1, the compound N was used as a charge transport material.
o. 5 in place of the indole compound of No. 5
No. 8 in the compound No. 8 In place of the benzidine compound No. 12, the compound No. A photoconductor was prepared by the same way as that of Example 1 except that 14 benzidine compound was used.

Comparative Example 1 In Example 1, the compound N was used as the charge transport material.
o. 5 and 1.5 parts of the indole compound of Compound No. 5
Compound No. 12 was replaced with 1.5 parts of the benzidine compound. A photoconductor was prepared by the same way as that of Example 1 except that only 3 parts of indole compound of No. 5 were used.

Comparative Example 2 In Example 1, the compound N was used as the charge transport material.
o. 5 and 1.5 parts of the indole compound of Compound No. 5
No. 12 instead of using 1.5 parts of the benzidine compound. A photoconductor was prepared by the same way as that of Example 1 except that only 3 parts of indole compound No. 8 were used.

Comparative Example 3 In Example 1, the compound N was used as the charge transport material.
o. 5 and 1.5 parts of the indole compound of Compound No. 5
No. 12 instead of using 1.5 parts of the benzidine compound. A photoconductor was prepared by the same way as that of Example 1 except that 3 parts of only 12 benzidine compound was used.

With respect to the photoreceptor thus manufactured,
Evaluate the sensitivity.
Changes in charge potential and residual potential when light and static elimination are repeated
The movement was examined. These measurements were performed using the Kawaguchi Electric Works static
An electric charging test apparatus EPA8100 was used. Exposure in the dark
Charged by performing corona discharge on body surface at -6kV for 10 seconds
And then exposed to white light with an illuminance of 2 lx to expose the surface potential
Is the exposure required to decay to half of the initial
Half-attenuation exposure E_1/2And evaluated the sensitivity (E _1/2of
The smaller the value, the better the sensitivity). In addition, the wavelength 780 of 1 μW
The surface potential after irradiating monochromatic light of
Rank. Next, charging, exposure, and static elimination are defined as one cycle.
Before repeating the repetition process 5000 cycles
The charge potential and residual potential were measured later. These measurement results
Are shown in Table 1.

[0036]

[Table 1]

As shown in Table 1, the indole compound alone was used as the charge transport material of the charge transport layer in comparison with the photoreceptors of Examples 1 to 4 in which an indole compound and a benzidine compound were mixed. The photoconductors of the photoconductors of Comparative Examples 1 and 2 used had a large fluctuation in the residual potential, and the photoconductor of Comparative Example 3 using the benzidine compound alone had a large fluctuation in the charged potential. The effect of mixing the two as the transport material is apparent.

Example 5 A conductive substrate was 30 mm long and 30 mm wide as in Example 1.
An aluminum plate having a thickness of 1 mm and a thickness of 1 mm was prepared. A coating solution obtained by dissolving 4.5 parts of a polyamide resin (“Daiamide T-171” manufactured by Daicel Co., Ltd.) in 150 parts of methanol is dip-coated thereon, and dried at a temperature of 90 ° C. for 20 minutes to form a film having a film thickness of 0. An undercoat layer of 2 μm was provided.

Next, the compound N as a charge transport material
o. 1.5 parts of the indole compound of Compound No. 2
1.5 parts of a benzidine compound of No. 13; 2.5 parts of a bisphenol Z-type polycarbonate resin (number average molecular weight: 50,000) as a binder resin; Was dissolved in 60 parts of dichloromethane, and 0.5 part of an X-type metal-free phthalocyanine as a charge generating substance was added thereto.
Dispersed for 0 hours. This dispersion was coated on the undercoat layer with a wire bar and dried at a temperature of 100 ° C. for 20 minutes.
A photosensitive layer having a thickness of 20 μm was formed, and a single-layer type photosensitive member having the configuration shown in FIG. 2 was produced.

Example 6 In Example 5, the compound N was used as a charge transport material.
o. 2.1 parts of the indole compound of Compound No. 2
Except for using 0.9 parts of the 13 benzidine compound,
A photoconductor was prepared in the same manner as in Example 5. Example 7 In Example 5, the compound N was used as a charge transport material.
o. No. 2 indole compound and 0.3 part of compound No.
Except for using 2.7 parts of 13 benzidine compound,
A photoconductor was prepared in the same manner as in Example 5.

Example 8 In Example 5, the compound N was used as a charge transport material.
o. In place of the indole compound of Compound 2,
9 using the indole compound of Compound No. 9 Compound No. 13 was replaced with Compound No. 13 A photoconductor was prepared by the same way as that of Example 5 except that 15 benzidine compound was used.

Comparative Example 4 In Example 5, the compound N was used as a charge transport material.
o. 2 and 1.5 parts of the indole compound
13 instead of using 1.5 parts of the benzidine compound. A photoconductor was prepared by the same way as that of Example 5 except that only 3 parts of indole compound of No. 2 were used.

Comparative Example 5 In Example 5, the compound N was used as a charge transport material.
o. 2 and 1.5 parts of the indole compound
13 instead of using 1.5 parts of the benzidine compound. A photoconductor was prepared by the same way as that of Example 5 except that only 3 parts of indole compound No. 9 were used.

Comparative Example 6 In Example 5, the compound N was used as a charge transporting substance.
o. 2 and 1.5 parts of the indole compound
13 instead of using 1.5 parts of the benzidine compound. A photoconductor was prepared by the same way as that of Example 5 except that only 3 parts of benzidine compound No. 13 were used.

With respect to the photoreceptor thus obtained,
The sensitivity was evaluated, and as the repetition characteristics, changes in the charged potential and the residual potential when charging, exposure, and static elimination were repeatedly performed were examined. For these measurements, as in the case of Example 1, the electrostatic charging tester EPA810 manufactured by Kawaguchi Electric Works, Ltd. was used.
0 was used. +6 kV corona discharge on photoreceptor surface in dark place
And then exposed to 2 lx of white light to determine the half-attenuated exposure E1 _{/ 2} , which is the amount of exposure required to attenuate the surface potential to half the initial value, to evaluate the sensitivity. (The smaller the value of E1 _{/ 2,} the better the sensitivity). Also, 2
The surface potential after irradiating lx white light for 10 seconds was defined as the residual potential. Next, a repetition process in which charging, exposure, and static elimination were defined as one cycle was repeated 5000 cycles, and the charged potential and residual potential before and after that were measured. Table 2 shows the measurement results.

[0046]

[Table 2]

As can be seen from Table 2, Comparative Examples using the indole compound alone as compared with the photoreceptors of Examples 5 to 8 in which the indole compound and the benzidine compound were used as the charge transporting substances in a mixture. The photoconductors of Nos. 4 and 5 have large fluctuations in the residual potential, and Comparative Example 6 using the benzidine compound alone was used.
In the photoreceptor of (1), the charge potential is greatly reduced, and the effect of mixing and using both as the charge transport material is apparent even in a single-layer type photoreceptor.

[0048]

According to the present invention, at least one kind of the indole compound represented by the general formula (I) and at least one kind of the benzidine compound represented by the general formula (II) are used as charge transport materials. A photosensitive member provided with a photosensitive layer comprising the same. As described above, by mixing the two as the charge transporting material, it is possible to obtain a photosensitive member having stable photoreceptor characteristics, in particular, a stable potential when used repeatedly.

The above-mentioned effects can be obtained regardless of the constitution of the photosensitive layer, either in a single-layer constitution or in a laminated constitution, and also when a subbing layer is provided between the conductive substrate and the photosensitive layer.

[Brief description of the drawings]

FIG. 1 is a conceptual sectional view of one embodiment of a photoreceptor of the present invention.

FIG. 2 is a conceptual sectional view of a different embodiment of the photoreceptor of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 conductive substrate 2 a laminated photosensitive layer 2 b single-layer photosensitive layer 3 undercoat layer 21 charge generating substance 22 charge generating layer 23 charge transporting substance 24 charge transporting layer

Continuation of the front page (56) References JP-A-53-31138 (JP, A) JP-A-62-163059 (JP, A) JP-A-3-43744 (JP, A) JP-A-4-124670 (JP) JP-A-3-1153 (JP, A) JP-A-4-265977 (JP, A) JP-A-63-271355 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB (Name) G03G 5/06

Claims (6)

(57) [Claims] 1. An electrophotographic photoreceptor comprising a photosensitive layer comprising a charge generating substance and a charge transporting substance on a conductive substrate, wherein the charge transporting substance is an indole compound represented by the following general formula (I): And an electrophotographic photosensitive member comprising a photosensitive layer containing at least one of the following and at least one of the benzidine compounds represented by the following general formula (II). Embedded image [In the formula (I), R 1 and R 2 each represent a hydrogen atom, an alkyl group having 1 to 9 carbon atoms, an aralkyl group, or an aryl group, and R 3 represents a hydrogen atom, 1 to 9 carbon atoms. Represents any one of three alkyl groups, alkoxyl groups, and halogen atoms. ] [In the formula (II), Z1 represents a hydrogen atom or a group having 1 to 1 carbon atoms.
Z2 and Z3 each represent any one of a hydrogen atom, an alkyl group having 1 to 2 carbon atoms, and a halogen atom. ] 2. The electrophotographic photoreceptor according to claim 1, wherein the photosensitive layer is a single layer containing a mixture of a charge generating substance and a charge transporting substance. 3. The electrophotographic photoreceptor according to claim 1, wherein the photosensitive layer comprises a laminate of a charge generating layer containing a charge generating substance and a charge transporting layer containing a charge transporting substance. 4. The electrophotographic photoreceptor according to claim 1, wherein the charge generating substance is a disazo pigment. 5. The electrophotographic photoreceptor according to claim 1, wherein the charge generating substance is an X-type metal-free phthalocyanine. 6. The electrophotographic photosensitive member according to claim 1, wherein an undercoat layer is provided between the conductive substrate and the photosensitive layer.